Recently, standardization has started to converge in the LTE (Long Term Evolution) system that is the 3.9G cellular telephone wireless communication system, and further, standardization has started in LTE-A (LTE-Advance, also referred to as “IMT-A”) that is the 4G wireless communication system further evolved from the LTE system. In LTE-A, further improvements are desired in transmission efficiency targeted for low-mobility users. In the LTE system, it is already determined that the single-user MIMO (Multi-Input Multi-Output) technique is adopted in downlink (communications from the base station apparatus to terminal apparatus), and in LTE-A, it is proposed to further increase the number of antennas, and thereby improve transmission efficiency.
Meanwhile, in uplink, with importance placed on loads of the high power amplifier (hereinafter, referred to as “HPA”) of the terminal apparatus, adopted as a communication scheme was DFT-S-OFDM (Discrete Fourier Transform Spread Orthogonal Frequency Division Multiplexing) with good PAPR (Peak to Average Power Ratio) characteristics. Then, adoption of single-user MIMO was postponed with increases in power consumption feared.
In the LTE-A system, it is expected that the MIMO technique will be adopted also in uplink to aim at improvements in transmission efficiency, and it is proposed to apply an OFDM (Orthogonal Frequency Division Multiplexing) system when MIMO is used. As the reason, it is considered that when the OFDM system is used, the maximum likelihood decision method called MLD (Maximum likelihood Detection) can be used with a feasible computation amount, and that best reception performance is obtained.
Further, Patent Documents 1 and 2 disclose examples of switching between access schemes. More specifically, proposed is a method of switching between OFDM that is of typical multicarrier signal and DFT-S-OFDM (described as “SC-FDM” in the documents) of single-carrier signal. Furthermore, as a criterion by which to switch, it is proposed that power headroom (hereinafter, referred to as “PH”) to saturation power in the HPA is used as a criterion value and switch between access schemes based on the criterion value.    Patent Document 1: Japanese Unexamined Patent Publication No. 2007-151059    Patent Document 2: International Publication No. WO/2008057969 Pamphlet